Tradescantia wrightii and T. pinetorum belong to section Tradescantia ser. Tuberosae D. R. Hunt and differ from the species of ser. Virginianae D. R. Hunt (species 1--19) by being geophytes (instead of hemicryptophytes) and in having the hilum much shorter than the seed (instead of ± equal to the seed). Tradescantia wrightii differs from T. pinetorum by its lack of root tubers, its glabrous leaves and internodes, and the absence of lateral inflorescences. The glandular hairs on the pedicels and sepal bases, much shorter than those of T. pinetorum, are easily overlooked.